The present invention generally relates to rotary furnaces and, more particularly, to a tilting rotary furnace system used in the reclamation of non-ferrous metals from scrap or dross and a method of operating the furnace.
There is an ever present demand for recovering usable material, such as non-ferrous metals, from scrap and waste items. During the recovery process, there are additional demands to decrease the amount of resources, especially fuel, required to convert the items into usable material and to decease the amount of waste by-product generated by the recovery process.
To date, the process of recovering non-ferrous metals, such as aluminum from batches of scrap material or dross material, is fairly inefficient. Aluminum scrap is obtained from a number of sources, such as waste aluminum from manufacturing facilities, industrial scrap, used automobile parts such as engine blocks, beverage containers and the like. Dross containing aluminum is often obtained as a byproduct from a manufacturing facility which uses molten metals. It is noted that dross typically has a lower aluminum content than scrap. Dross, as used herein, means the solid scum that forms on the surface of a metal when molten or during melting and is largely the result of oxidation, due to conversion of aluminum fines (small particles) to aluminum oxide, but also includes aluminum, dirt and impurities that rise to the surface of the mixture. Dross also includes salt and/or flux used as part of the previous melting process which can be potassium chloride (KCl), sodium chloride (NaCl) or other salt such as NaF, NaBr, KF and FBr. Dross also includes waste or foreign matter mixed with a substance or what is left as a residue after the substance has been used or processed.
Examples of non-ferrous recovery metal devices can be found in U.S. Pat. Nos. 5,527,380 and 5,540,752. However, these examples have not generated proven, repeatable results. In addition, these and other devices making up the current state of the art with regard to aluminum recovery have slow throughput (i.e., melt rate) with a low recovery rate in terms of the weight of recovered metal versus the beginning weight of the scrap. The current recovery devices and methods have relatively high conversion costs and use a considerable amount of fuel (e.g., 65 m3 of natural gas per metric ton of scrap and flux material). They also use a considerable amount of flux to retard oxidation. The current recovery devices and methods also generate a considerable amount of waste by-product in the form of slag (slat cake). The slag is generally not useful and requires disposal, which consumes valuable landfill space.
According to an aspect of the present invention, a furnace system for recovering a non-ferrous metal from a charge of material containing the metal, includes: a furnace chamber having walls defining a refractory chamber, the refractory chamber receiving the charge of material and the metal contained in the charge of material being heated into a flowable mode in the refractory chamber; and at least one paddle projecting from an interior surface of the furnace chamber toward an interior of the refractory chamber.
According to another aspect of the present invention, a furnace system for recovering a non-ferrous metal from a charge of material containing the metal, includes: a furnace chamber having walls defining a refractory chamber, the refractory chamber receiving the charge of material and the metal contained in the charge of material being heated into a flowable mode in the refractory chamber, the walls of the furnace chamber further defining an inlet passage to provide access to the refractory chamber; and a door having a closed position adjacent the inlet passage and an open position to provide access to the inlet passage, the door having a plurality of rollers engaging a rolling surface disposed on the furnace chamber adjacent the inlet passage, the door coupled to a support structure with a suspension, the rollers and suspension maintaining the door in a closed position during operation of the furnace system.
According to another aspect of the present invention, a furnace system for recovering a non-ferrous metal from a charge of material containing the metal, includes: a furnace chamber having walls defining a refractory chamber, the refractory chamber receiving the charge of material and the metal contained in the charge of material being heated to a flowable mode in the refractory chamber; a motor coupled to the furnace chamber and rotating the furnace chamber about a longitudinal axis; and a control unit, the control unit monitoring torque to rotate the furnace chamber as an indication of viscosity of the charge of material.
According to another aspect of the present invention, a method of operating a furnace system for recovering non-ferrous metal from a charge of material containing the metal, the furnace system having a furnace chamber defining a refractory chamber and an inlet passage for providing access to the refractory chamber, includes the steps of: charging the refractory chamber with at least one charge of material; rotating the furnace chamber; heating the charge of material into a flowable mode; and monitoring the viscosity of the charge of material by measuring torque to rotate the furnace chamber.
According to another aspect of the present invention, a method of operating a furnace system for recovering non-ferrous metal from a charge of material containing the metal, the furnace system having a furnace chamber defining a refractory chamber and an inlet passage for providing access to the refractory chamber, includes the steps of: charging the refractory chamber with an amount of charge material; rotating the furnace chamber; supplying heat energy to heat the charge of material into a flowable or near molten mode; and stopping the supply of heat energy after a predetermined amount of heat energy has been supplied, the predetermined amount of heat energy based on the amount of the charge of material.
According to another aspect of the present invention, a method of operating a furnace system for recovering non-ferrous metal from a charge of material containing the metal, the furnace system having a furnace chamber defining a refractory chamber and an inlet passage for providing access to the refractory chamber, includes the steps of: charging the refractory chamber with at least one charge of material; rotating the furnace chamber about a longitudinal axis of the furnace chamber; providing faceted surfaces on the interior of the interior furnace chamber to define the refractory chamber; and introducing heat energy into the refractory chamber at an angle to the longitudinal axis of the furnace chamber so that heat produced by the flame is reflected off of the faceted surfaces to provide a heat bath adjacent a top surface of the charge of material and heating the charge of material into a flowable mode.
According to another aspect of the present invention, a method of operating a furnace system for recovering non-ferrous metal from a charge of material containing the metal, the furnace system having a furnace chamber defining a refractory chamber and an inlet passage for providing access to the refractory chamber, includes the steps of: charging the refractory chamber with at least one charge of material; rotating the furnace chamber about a longitudinal axis of the furnace chamber; heating the charge of material into a flowable mode; and providing at least one paddle projecting from an interior surface of the furnace chamber towards an interior of the refractory chamber, the at least one paddle effective to break up and submerge the at least a portion of a portion of a slag material formed on a top surface of the charge of material.